Couple things to consider here. Don't use monofilament line(!). It behaves badly in the cold, is hard to handle, causes tripping hazard (because it's clear, coils and blows around) . it also has ALLOT of stretch which makes setting the hook ( by hand) difficult. Just about all my tip-ups are set up with 50-60 yards of 30 - 50# Dacron with a 6' monofilament tip. ( Which is a very common set-up in this area) This gives you enough to fish most depths and leaves reserve on the spool for the fish to run. ( While your running to get to the trap!)
The heavier line is best so as not to cut your hands when setting the hook or "playing the fish". However, too heavy ( over 80-100#, and fish will often fee' the drag of teh line and drop the bait. Dacron is best because it has no stretch and has no memory so it lays flat on the spool & ice. Braided nylon is cheaper but suffers from streatch. A 1000 yd spool of dacron "green spot" trolling line (enough for 20 traps) should run $50-$60 at any local shop/ bass pro shops/Cabelas/Ebay. If you scrounge, you might even find some used line off someones trolling reels. It's common stuff.
p.s. Thread a common shirt button onto each line (through two holes) before attaching terminal hardware. Then you can slide the button up and down the line to use it as a marker for setting bait depth. This helps allot in setting traps properly.
hth